1. Field of the Invention
The invention is directed to a laser scanning microscope or spectral detector having a detection beam path and at least first imaging optics which image spectrally dispersed sample light in a Fourier plane in such a way that the individual spectral components of the sample light are spatially separated from one another therein. A micromirror arrangement is provided in this plane, and a spectrally selective change in direction of the detection beam is carried out by controlling the micromirrors, where a useful light component of the detection beam arrives on a detector. In order to improve the spectral selection, at least one second micromirror arrangement and a 1:1 imaging of the first micromirror arrangement in the second micromirror arrangement is provided. Alternatively, the same micromirror arrangement is passed at least twice, where, in the light path between the first pass and second pass, a spatial offset of the light beam of at least the first pass and second pass is generated on the micromirror arrangement by optical means.
2. Description of Related Art
U.S. Pat. No. 5,504,575B1 describes an optical arrangement and method for spectral characterization of an input beam by means of a spatial light modulator (SLM). In a construction with a micromirror arrangement (digital mirror device—DMD), only selected spectral components are reflected in direction of the detector.
U.S. Pat. No. 6,750,036B2 describes an arrangement for spectrally resolved detection of the fluorescence signal of a cellular specimen with a plurality of dyes which are excited simultaneously. The object light is split spectrally and is received by a suitable array detector. The spectrum of the object light is received without filtering and can contain spectral components of excitation light.
U.S. Pat. No. 6,809,815B2 and U.S. Pat. No. 6,954,306B2 show optical arrangements for spectrally selective detection of the object light in a fluorescence microscope which contain a dispersive element for angular splitting of the spectral components of the object light. These arrangements act as bandpass filters and do not allow a flexible spectral filtering of the object light.
U.S. Pat. No. 5,886,784, U.S. Pat. No. 6,852,967B2 and U.S. Pat. No. 6,977,724B2 describe constructions with displaceable diaphragms. Accordingly, this arrangement allows simultaneous detection of a plurality of spectral regions of the fluorescent light. However, the quantity of detected regions is limited by the quantity of detector diaphragm units. Also, since the diaphragms employed only provide a bandpass filter function, this arrangement does not allow a flexible filtration of the spectrum of the object light.
DE 102004031049A1 describes an arrangement for the simultaneous detection of a plurality of spectral regions of the object light only by means of a one-channel detector. The selection of the radiation components to be detected is carried out by means of a blocking element. The unwanted components are blocked out of the detection beam path. This approach allows flexible filtering of the object light. However, due to the fact that only the integrated intensity is measured over all of the detected regions in this arrangement, no spectral characterization of the fluorescence is possible in this case. Further, a substantial thickness of the individual webs causes losses in intensity of the fluorescent light.
In DE 10102033B4, the object light is split spectrally and imaged on a multichannel detector. Reduction means are arranged in front of the dispersive element. However, since the filter function is only determined by the characteristics of the means used for reduction, a flexible spectral filtration of the object light is impossible.
U.S. Pat. No. 6,377,344B2 describes a device by which the illumination beam path, object beam path and detection beam path in a microscope are separated from one another purely geometrically. Additional subsequent filtration of the object light in front of the detector is necessary in this case.
DE 102007002583A1 describes a main color splitter based on the same approach as the arrangements and methods described in U.S. Pat. No. 6,377,344B2. The illumination beam path, object beam path and detection beam path in a microscope are separated from one another purely geometrically. For this purpose, a microstructured element comprising a DMD unit is used in the Fourier plane of a 4f arrangement to couple the desired spectral components of the illumination beam into the microscope in a specific manner. The suppression efficiency for scattered light is limited so that there is a need for additional subsequent filtering.
U.S. Pat. No. 7,212,338B2 describes the implementation of a spectral detector in a microscope, where the spectrum of the sample light is received by means of a detector. For this purpose, the light which is emitted by the sample and scattered at the sample is divided into its spectral components and imaged on a selectively switchable micromirror arrangement (digital mirror device—DMD) by means of suitable optics. The unwanted wavelengths of the beam are not detected. This enables additional suppression of the excitation light scattered at the sample. To capture a spectrum of the object light, the individual spectrally resolved components of the radiation are imaged in the detector successively in time. The intensities of the individual spectral regions give the total spectrum.
U.S. Pat. No. 6,396,053B1, U.S. Pat. No. 6,459,484B1 describe optical arrangements for simultaneous detection of a plurality of spectral regions of fluorescent light in a microscope. For this purpose, the object light is spectrally resolved on an arrangement comprising a plurality of deflecting micromirrors. Each micromirror is characterized by a plurality of tilting angles. Because of the scattering at the edges and surfaces of the individual micromirrors, the efficiency of suppression is limited.
U.S. Pat. No. 7,190,451B2 describes a further development of the optical arrangements described in U.S. Pat. Nos. 6,396,053B1 and 6,459,484B1. The device is augmented by a collimating lens which is inserted in the detection beam path between the micromirror unit and the detector. Accordingly, the individual spectrally resolved partial beams are imaged on the detector in parallel. Because of the scattering at the edges and surfaces of the individual micromirrors, the efficiency of suppression is likewise limited in this case to only about 3 OD.